LibWeb: Don't drop single <br/> lines

Previously, when having inline contexts consisting of just a `<br/>`
tag, we would not create a line box.

Ensure that there is always a line box when a line is explicitly being
broken and also ensure it won't be trimmed due to being empty.

This will a fix a number of sites that use `<br>` tags for layouts
between block elements (even though the spec says they shouldn't).

2 files changed, 6 insertions, 2 deletions

diff --git a/Userland/Libraries/LibWeb/Layout/LineBox.h b/Userland/Libraries/LibWeb/Layout/LineBox.h
index a333943b63..8bfd6a3f91 100644
--- a/Userland/Libraries/LibWeb/Layout/LineBox.h
+++ b/Userland/Libraries/LibWeb/Layout/LineBox.h
@@ -28,7 +28,7 @@ public:
     void trim_trailing_whitespace();
 
     bool is_empty_or_ends_in_whitespace() const;
-    bool is_empty() const { return m_fragments.is_empty(); }
+    bool is_empty() const { return m_fragments.is_empty() && !m_has_break; }
 
 private:
     friend class BlockContainer;
@@ -40,6 +40,7 @@ private:
     CSSPixels m_height { 0 };
     CSSPixels m_bottom { 0 };
     CSSPixels m_baseline { 0 };
+    bool m_has_break { false };
 };
 
 }
diff --git a/Userland/Libraries/LibWeb/Layout/LineBuilder.cpp b/Userland/Libraries/LibWeb/Layout/LineBuilder.cpp
index b09adc0fe7..f02278b1a9 100644
--- a/Userland/Libraries/LibWeb/Layout/LineBuilder.cpp
+++ b/Userland/Libraries/LibWeb/Layout/LineBuilder.cpp
@@ -26,6 +26,9 @@ LineBuilder::~LineBuilder()
 
 void LineBuilder::break_line(Optional<CSSPixels> next_item_width)
 {
+    auto last_line_box = ensure_last_line_box();
+    last_line_box.m_has_break = true;
+
     update_last_line();
     size_t break_count = 0;
     bool floats_intrude_at_current_y = false;
@@ -305,7 +308,7 @@ void LineBuilder::remove_last_line_if_empty()
 {
     // If there's an empty line box at the bottom, just remove it instead of giving it height.
     auto& line_boxes = m_containing_block_state.line_boxes;
-    if (!line_boxes.is_empty() && line_boxes.last().fragments().is_empty()) {
+    if (!line_boxes.is_empty() && line_boxes.last().is_empty()) {
         line_boxes.take_last();
         m_last_line_needs_update = false;
     }